A generally used printed circuit board (PCB) is an electrical printed circuit board and is used by coating a substrate on which a copper thin circuit is formed, and inserting various kinds of component into the substrate to transmit electric signals. Since the conventional electrical printed circuit board has a low electric signal transmitting ability of the substrate compared to a components treating ability of the electric device, there was a problem in the transmission of transmit signals.
In particular, these electric signals are sensitive to outside circumstances and a noise phenomenon is generated. Thus, this becomes a large obstacle in electrical appliances which require high precision. Thus, to complement it, an optical printed circuit board using an optical waveguide instead of the electrical printed circuit board having the metallic circuit such as Cu has been developed, high precision and high-tech equipment, which is more stable to jamming, the noise phenomenon and the like, can be produced.
According to conventional arts, in the case of an optical printed circuit board, as disclosed in Prior Reference 1 (Publication No. 10-2011-0038522), an optical waveguide is produced by bending optical fiber at 90°, as disclosed in Prior Reference 2 (Publication No. 10-2010-0112731), the optical waveguide is produced by forming a mirror at an internal core layer, or as disclosed in Prior Reference 3 (Publication No. 10-2011-0038524), the optical printed circuit board is produced by manufacturing the printed circuit board and a light connecting module, separately, and inserting the separately manufactured light connecting module into the manufactured printed circuit board.
However, in Prior Reference 1, when optical printed circuit board is manufactured, the structure, in which the optical fiber is bent at 90° to connect the optical fiber with a signal transmitter TX and a signal receiver RX, is applied thereto, and during bending the optical fiber at 90°, optical loss is generated. Also, during a laminating process for burying layers in the printed circuit board, in a case where a step difference is present between the layers of the printed circuit board may occur and a bent region of the optical fiber, transmission loss is generated due to a high pressure.
Also, a total thickness of the optical module including the bent region increases a total thickness of the printed circuit board.
Also, in Prior Reference 2, it is problematic that it would be difficult to maintain an angle of a core exposed to the outside due to deformation (rolling or twisting) caused by heat, pressure and resin flow at laminating during the process for burying the layers in the printed circuit board.
Moreover, according to Prior Reference 3, due to a limitation in bend and a limitation in length and thickness of the manufactured optical waveguide, there is difficulty to overcome a limitation of the thin and small printed circuit board. Furthermore, as the printed circuit board and the optical connection module are manufactured separately, it is problematic that the process of manufacturing the optical circuit board is complex.